Coated plastic articles



United States Patent 3,274,026 COATED PLASTIC ARTICLES Arthur S. Nyquist, Darien, Conn., assignor to American Cyanamid Company, Stamford, Conn, a corporation of Maine No Drawing. Filed June 19, 1962, Ser. No. 203,450 18 Claims. (Cl. 117-138.8)

This invention relates to a novel method of imparting resistance to stains, particularly those made by coffee and tea, to heatand pressure-consolidated articles prepared from aminoplast resinous compositions. This invention also relates to the novel stain-resistant articles, such as molded tableware articles, produced according to my novel method, and further relates to the stain-retarding compositions, used in preparing such articles.

The many excellent properties possessed by aminoplast resins, and in particular by aminotriaZine-aldehyde resins such as melamine-formaldehyde resins, have led to their widespread use in the molding and laminating fields. More particularly, these thermosetting or heat-harden able resins possess, in the cured or thermoset state, superior break-resistance, resistance to water and other solvents, to softening or other internal heat-failures, to cracking when exposed to electrical stress, and to surface failures such as loss of gloss, discoloration or crazing due to heat and light, all of which features render them especially suitable for the preparation of heatand pressure-consolidated molded and laminated articles.

However, heatand pressure-consolidated articles such as laminated table, counter and bar tops, molded cups, saucers, plates, and the like, prepared from conventional thermosetting aminoplast resins such as rnelamine-formaldehyde resinous condensates do possess one deficiency which detracts from their overall excellence. Articles of this type are susceptible to various kinds of stains. Coffee and tea are among the worst offenders in this respect, but other substances, for example, the juices of various fruits and vegetables, such as raspberry, grape, and beet juices, to mention just a few, soft drinks (e.g., cola drinks), cocoa, and the like, also leave stains which detract from the appearance, although not the durability, of such molded and laminated articles, and which in many cases are diflicult to remove even if attended to immediately.

This propensity of conventionally prepared heatand pressure-consolidated aminoplast resin-containing laminated and molded articles for staining has limited, in many cases, the extent to which such articles have found acceptance in many important areas of everyday use. For example many people, and especially restaurateurs and other large-volume users of dinnerware, have been reluctant to replace chinaware with high-quality tableware made from thermosetting melamine-formaldehyde resinous compositions, despite the latters many obviously superior properties.

I have now discovered that thermosetting resinous compositions comprising a blend of a highly alkoxymethylated melamine, such as hexakis(methoxymethyl) melamine, with an epoxy resinous material obtained by reacting a polyhydric phenol, e.g., bisphenol A (2,2-bis- 4-hydroxyphenylpropane), with an epihalohydrin, such as epichlorohydrin, when applied to the surfaces of heatand pressure-consolidated cured or partially cured articles prepared from conventional thermosetting aminoplast resinous compositions, such as melamine-formaldehyde resinous compositions, and cured thereon to a substantially insoluble and infusible state by means of an acid curing catalyst, impart substantial stain-resistance to said articles.

It is, therefore, an object of my invention to provide a novel method of imparting stain-resistance to heatand pressure-consolidated articles prepared from thermosetting aminoplast resinous compositions, particularly those prepared from melamine-formaldehyde resinous compositions.

It is also an object of my invention to prepare heatand pressure-consolidated articles from thermosetting aminoplast resinous compositions, and particularly from melamine-formaldehyde resinous compositions, wherein the surfaces of said articles have been provided with a substantially insoluble and infusible cured, adherent coating which is resistant to staining by common foods and beverages.

A further object of my invention is to provide heatand pressure-consolidated molded and laminated articles, prepared from thermosetting aminoplast resinous compositions such as melamine-forrnaldehyde resinous compositions, which have been coated with a substantially insoluble and infusible cured, adherent, stain-resistant coating comprising the resinous reaction product of a highly alkoxymethylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, such as hexakis(methoxymethyl)melamine, and an epoxy resinous material obtained by reacting a polyhydric phenol, such as bisphenol A, with an epihalohydrin, such as epichlorohydrin.

A still further object of my invention is to provide stain-retardant compositions of matter useful in imparting stain-resistance to heatand pressure-consolidated articles prepared from thermosetting aminoplast resinous compositions, particularly those prepared from melamineformaldehyde resinous compositions.

These and other objects of my invention will be discussed more fully hereinbelow.

The thermosetting resinous compositions employed in the practice of the present invention, which may also be designated as potentially stain-retardant compositions, comprise, first of all, blends of two essential ingredients. The first of these is a highly alkoxymethylated melamine represented by the general formula:

MF A

wherein M represents melamine, the starting material, F represents the degree to which the melamine starting material has been methylolated, with x representing a number between about 3 and 6, inclusive, preferably a number between about 5 and 6, inclusive, and A represents the degree to which the methylol groups of the polymethylolmelamine intermediate have been alkylated with lower alkyl groups containing from 1 to 4 carbon atoms, such as methyl, ethyl, propyl, n-butyl, and the like, to provide alkoxymethyl groups containing from 2 to 5 carbon atoms in the highly alkoxymethylated melamine final product, with y representing a number between about 3 and 6, inslusive, preferably a number between about 5 and 6, inclusive, such that there no more than about one unalkylated methylol group present in the highly alkoxymethylated melamine. Thus, the highly alkoxymethylated melamines employed in the practice of the present invention range from the hexa-alkyl ethers of hexamethylolmelamine, such as hexakis(methoxymethyDmelamine and the like, which represent the highest degree of methylolation and alkylation obtainable, to the trialkyl ethers of trimethylolmelarnine, such as the trimethyl ether of trimethylolmelamine and the like. Furthermore, as is evident from the general formula and the values of x and y given above, one can use mixtures of these highly alkoxymethylated melamines, e.g., a mixture of hexakis(methoxymethyl)melamine .and the penta methyl ether of hexamethylolmelamine, and the like. In such cases x and y represent average values for the degree of rnethylolation and alkylation. Hexakis(methoxymethyl)melamine or mixtures containing a major amount thereof together with minor amounts of other highly methoxymethylated melamines having slightly lower degrees of methylolation and rnethylation are preferred for use in practicing the present invention.

The highly alkoxymethylated melamines are prepared by methods which are :so well known in the art that it is not necessary that they be set forth in great detail herein. In general, these conventional methods involve the basic steps of reacting melamine with aqueous formaldehyde in mol ratios ranging from about 6.5 to about 20 mols or more of formaldehyde per mol of melamine to form polymethylolmelamines; removing the bulk of the water from the thus-formed polymethylolmelamines, and thereafter reacting the polymethylolmelamines under acidic conditions with from about to about 30 mols of a lower alkanol, such as methanol, ethanol, propanol, and the like, per mol of melamine strating material. Various modifications .and improvements of this basic process have been developed, such as those set forth in U.S. Patents Nos. 2,715,619 to Suen et al. and 2,918,452 to Kun et al.

The second essential ingredient of my potentially stainretardant compositions is an epoxy resinous material, preferably but not necessarily a solid epoxy resinous material, prepared by reacting a polyhydric phenol with an epihalohydrin, such as epichlorohydrin, epibromohydrin, epiiodohydrin, and the like. Among the polyhydric phenols which can be used in preparing these epoxy resinous materials are dihydric phenols represented by the general formula:

R1 -Q HO I t OH wherein the phenolic hydroxy groups may be in any of the 2,2; 2,3; 2,4; 3,3; 3,4 or 4,4 positions on the aromatic nuclei, and each of R and R represent hydrogen, an alkyl group, such as methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, pentyl, isopentyl, hexyl, isohexyl, and the like; a cyclo(lower)alkyl group, such as a cyclohexyl or substituted cyclohexyl group, e.g., methyl-, ethyl-, propyl-, butyl-, pentyland hexyl-substituted cyclohexyl, or an aromatic group, such as phenyl, tolyl, xylyl, and the like, with the total number of carbon atoms in the substituents represented by R and R not exceeding 14. In addition, the phenolic rings may have other substituents besides the hydroxyl groups, for example lower alkyl groups containing from 1 to 4 carbon atoms, i.e., methyl, ethyl, propyl, isopropyl, butyl, sec-butyl and tert-butyl groups, or halogen atoms, i.e., fluorine, chlorine, bromine or iodine.

An illustrative but by no means exhaustive listing of dihydric phenols falling within this general formula includes 4,4-dihydroxydiphenylmethane, 4,4-dihydroxydiphenyldimethylmethane (bisphenol A), 2,4'-dihydroxydiphenylethylmethane,

3 ,3 '-dihydroxydiphenyldiethylmethane,

3 ,4'-dihydroxydiphenylmethylpropylmethane,

2,3 '-dihydroxydiphenylethylphenylmethane, 4,4-dihydroxydiphenylpropylphenylmethane, 4,4--dihydroxydiphenylbutylphenylmethane, 2,2-dihydroxydiphenylditolylmethane, 4,4'-dihydroxydiphenyltolylmethylmethane,

and the like. Other polyhydric phenols which may also be co-reacted with an epihalohydrin to provide epoxy resinous materials which may be employed in the practice of the present invention are such compounds as resorcinol, hydroquinone, substituted hydroquinones, e.g., p-tertbutylhydroquinone, and the like, and indanols such as those disclosed in US. Patent No. 2,754,285 to Petropoulos.

These epoxy resins, many of which are available commercially, as well as methods for their preparation, are so well known in the art, and have been disclosed so many times, particularly in the patent literature, that only the most cursory treatment of such methods need be given here. In general, when preparing these resins, the reaction is usually carried out in the presence of an amount of an alkaline material, e.g., sodium hydroxide, sufficient to combine with the halogen released by the epihalohydrin during the course of the reaction. The amount of epihalohydrin used is generally in excess of the stoichiometric quantity required for reaction with the polyhydroxy phenol. The resulting resinous reaction products may contain free terminal hydroxyl groups or terminal hydroxyl groups and terminal epoxy groups, and will vary in molecular weight depending on the reactants employed, the relative amounts thereof, and the extent to which the reaction is carried out. These thermosetting epoxy resinous materials are generally soluble in solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, .and the like.

The potentially stain-retardant compositions of the present invention are prepared by blending together from about 10% to about 70% by weight, preferably from about 25% to about 50% by weight, based on the total weight of highly alkoxymethylated melamine and epoxy resinous material, of the highly alkoxymethylated melamine and, correspondingly, from about to about 30% by weight, preferably from about 75% to about 50% by weight, based on the total weight of highly alkoxymethylated melamine and epoxy resinous material, of said epoxy resinous material. Blending can be accomplished by milling a mixture of these tWo ingredients in the absence of a solvent on a mill, e.g., a two-roll rubber mill, at a temperature of from about 80 C. to about C. until a substantially homogeneous blend is obtained, or by merely dissolving or dispersing either or both of these two ingredients in a suitable inert organic solvent and then blending the-m together by any suitable mechanical means, such as in a laboratory mixer, to obtain a substantially homogeneous blend.

For certain applications dry blends, such as those obtained by milling mixtures of these two essential ingredients, will be pulverized to fine, powdery materials, for example by ball milling, and used as such. In other cases, these powdered materials will be dissolved in a suitable organic solvent and used in this form to treat the surfaces of 'heatand pressure-consolidated aminoplast articles. Similarly, blends prepared from solutions of the two ingredients may be either used as such for certain applications, with or without the further addition of organic solvent, or the solvent used in preparing the blend may be evaporated and the resulting dry, homogeneous blend may then be pulverized to a fine powder and used in this form as a potentially stain-retardant composition.

As previously indicated, an acid curing catalyst will be incorporated into my potentially stain-retardant compositions prior to their use in order to facilitate their cure. A particularly preferred class of acid curing catalysts includes mineral acids, such as phosphoric acid and the like, organic acids such as phthalic, p-toluenesulfonic, benzenesulfonic, and the like, acid salts, e.g., the morpholine and N-methyl morpholine salts of p-toluenesulfonic and benzenesulfonic acids, and mixtures thereof, e.g., a mixture containing from about 30% to about 70% of p-toluenesulfonic acid and, correspondingly, from about 70% to about 30% of the N-methyl morpholine salt of p-toluenesulfonic acid. The optimum curing conditions are modified to some extent by the choice of the particular catalyst. Thus, a more active catalyst, e.g., p-toluenesulfonic acid, should be used in lower concentrations than a less reactive material, e.g., phthalic acid or the aforementioned blends of p-toluenesulfonic acid and its N-methyl morpholine salt, such as a 65/35 salt/ acid blend. In general, however, these acid curing catalysts may be employed in amounts ranging from about 0.2% to about 2% by weight, based on the total weight of the resinous blend, which blend may be in either solution or powder form at the time the acid curing catalyst is introduced.

It should also "be noted at this point that the procedures outlined above for the preparation of my potentially stainretardant compositions merely represent preferred methods of preparation, and should not be considered a limitation on my inventive concept, inasmuch as any suitable method of compounding the essential ingredients of my compositions may be employed without detracting from the spirit and scope of the invention.

Similarly, any of a number of suitable methods may be employed in applying my potentially stain-retardant compositions to the surfaces being treated and curing said compositions thereon.

One such method involves the use of solutions of the potentially stain-retardant compositions in inert organic solvents. Among such solvents there are included aromatic hydrocarbons, such as benzene, toluene, xylene, and the like; aliphatic monocarboxylic acid esters of aliphatic monohydric alcohols, such as butyl acetate, amyl acetate, hexyl acetate, ethyl butyrate, and the like; aliphatic monocar-boxylic acid monoesters of the lower alkyl monoethers of dihydric alcohols, such as the monoacetates of the methyl, ethyl, propyl and butyl monoethers of ethylene glycol, diethylene glycol, and the like; aliphatic monocarboxylic acid diesters of dihydric alcohols, such as the diacetates of ethylene glycol, diethylene glycol, and the like; ketones, such as acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl kctone, cyclohexanone, and the like; halogenated organic solvents, such as ethylene dichloride, chlorobenzene, and the like, and nitroparafiins, such as nitropropane and the like. As might be expected, mixtures of these solvents may also be employed and, in some instances, will even be preferred.

The relative amounts or" the solvent and the substantially homogeneous "blend of a highly alkoxymethylated melamine and an epoxy resinous material which are employed may be varied over a wide range, depending on the viscosity desired in the coating composition, which in turn will depend on the method to be employed in applying the composition to the surfaces to be treated. For instance, if the composition is to be applied using a doctor knife or similar spreading means, relatively viscous solutions or, in some cases, almost paste-like materials, will be prepared. In such a case, relatively small amounts of solvent are needed. If, on the other hand, the composition is to be applied by spraying, by brushor rollercoating, or by dipping the article therein, larger amounts of solvent will be employed. In general, the amount of solvent employed will be such that the substantially homogeneous blend will be present in solution at a solids content ranging from about 5% to about 95% by weight.

Where solutions of my potentially stain-retardant compositions in inert organic solvents are formulated for use in dip-, flow-, brushor roller-coating heatand pressureconsolidated aminoplast articles it may be desirable, in certain instances, to add to such solutions minor amounts, e.g., amounts ranging from about 0.1 to about 1 part by Weight, based on the total weight of the solution, of conventional levelling agents, such as butylated melamineformaldehyde resins, butylated urea-formaldehyde resins, silicone oils, and the like, in order to counteract any possible tendency towards cratering or pinholing in the final thermoset coating. Ordinarily, this expedient will not be necessary where solutions of my potentially stainretardant compositions are applied using conventional spray-coating techniques.

It the substantially homogeneous blends are to be used to provide clear stain-resistant coatings, no colorant need be used. However, if it is desired to produce colored coatings a wide variety of pigments, dyes and colorants of all descriptions may be incorporated in conventional 6 amounts into said blends to provide the desired effect.

Following the application of the solution of my potentially stain-retardant composition to the amino-plast surface being treated, the coated article is first let stand for a period of time suificient to evaporate all or at least part of the inert solvent and also to allow the coating to level out, e.g., the coated cup can be subjected to air drying at room temperature, and is then placed in an oven and heat-treated, at temperatures ranging from about C. to about C. for from about 5 to about 30 minutes, to cure the thermosetting coating to a substantially insoluble, infusible, stain-resistant form. The drying time prior to heat-treating may be accelerated if desired, for example by the use of a suitable drying apparatus or by applying the coating composition to the heatand pressure-consolidated aminoplast article as it comes from the mold or press.

Another method which is particularly adapted to the preparation of aminoplast molded articles coated with the stain-resistant compositions of the present invention involves a technique which may be termed overglaze molding and which may be best understood by first briefly considering the procedure customarily followed in the conventional methods of preparing heatand pressureconsolidated molded articles from amino-plast resinous compositions such as thermosetting melamine-formaldehyde resinous compositions.

The thermosetting aminoplast resinous molding materials employed in the usual commercial molding practices are prepared by first impregnating a fibrous filler, such as chopped tit-cellulose, with a thermosetting aminoplast resin in syrup form, drying the impregnated material to a low volatile content, usually in the order of about 10% or less, converting the dried material to a fine, flufiy powder While blending it with various commonly employed additives, such as curing catalysts, pigments, mold lubricants, and the like, and finally densifying and granulating the powdered molding composition, thus converting it to a form especially suited for commercial molding techniques.

In such techniques, the common practice is to first shape the granular molding composition into a pre-formed article which approximates the shape the article will assume in its final form. This pre-forming step may be carried out either in a press or mold specifically designed for pre-forming or in a conventional molding press, either with or without the application of heat, to result in a preformed article whose resin content either remains uncured or becomes only partially cured, thus providing for the subsequent application of a decorative overlay, if desired. Decorative overlays comprising a single sheet or foil of high grade ct-cellulose paper or similar fibrous material impregnated with a thermosetting aminoplast resin of the type found in the pre-form and imprinted with an ornamental design are usually employed to provide a decorative efiect to relatively flat molded pieces, such as dinner plates, saucers, and the like, and are ordinarily not used with deep-draw molded articles such as cups, bowls, and the like. The pre-formed article is of a somewhat porous nature, and should contain slightly more resinous material than will be retained by the article when it assumes its final molded form. This is to insure that the mold used in the final molding operation will be substantially filled, with the usual provision being made for a small amount of flashing.

Ordinarily, the pre-formed article, either with or without a decorative overlay, is then placed in a molding press and molded, under suitable conditions of heat and pressure, to its final molded form. The overglaze molding technique employed in preparing aminoplast molded articles coated with the stain-resistant compositions of the present invention represents a slight departure from this common practice, in that the pro-formed article is first molded under suitable conditions of heat and pressure until the point is reached at which, for the first time, the

' degree of cure accomplished is such that the mold can be opened Without damaging the article being molded or having it stick to the opening portion of the mold. An article which has reached this degree of cure can be termed a pre-molded article. The time required to reach this point in the curing cycle will depend on many factors, e.g., the design of the mold, the nature of the composition being molded, the temperature and pressures used, etc., and will vary to some extent for each different molding operation encountered, but in general, it will usually be about 30 seconds or more after the start of the molding cycle. At this point, the mold is opened and an amount of my potentially stain-retardant composition, either in powdered form or as a solution in an inert solvent, suflicient to ultimately produce a thermoset coating of a desired thickness on the surfaces being treated is placed on the pre-molded article. Then, the mold is again closed, heat and pressure are applied, and the curing of both the pre-molded article and the potentially stain-retardant composition is carried to substantial completion.

Coatings of the stain-resistant compositions of the present invention may be applied to heatand pressureconsolidated aminoplast resin articles in a Wide range of thicknesses. The thickness of a particular coating applied by any suitable method, including those described hereinabove, can be regulated by many factors, including those inherent in the particular coating process itself, e.g., the viscosity of the treating solution and the time of contact in the case of coatings applied from solution. Stain-resistance can be obtained from coatings or films of a fraction of a mil in thickness. However, depending on the degree of abrasion resistance required in the coated article, coatings or films of from about 0.2 to about 1 mil or higher will usually be applied.

Thermosetting aminoplast resins of the type employed in the preparation of the heatand pressure-consolidated articles treated in accordance with the practice of the present invention are synthetic resins prepared by the condensation reaction of an amino (including imino) or amido (including imido) compound with an aldehyde. Resinous condensates of this type, as well as methods for their preparation, have been shown innumerable times in the prior art, and adequate disclosures of them may be found in, for example, US. Patents Nos. 2,197,357, 2,310,004 and 2,328,592 to Widmer et al. and 2,260,239 to Talbot. The present invention is concerned particularly with the treatment of molded and laminated articles prepared from aminoplast resins of the type wherein one or more aminotriazines containing at least two amidogen groups, each having at least one aldehyde-reactable hydrogen atom attached to the amidogen nitrogen atom, e.g., melamine, have been reacted with an aldehyde, such as formaldehyde, to yield a potentially thermoset resinous condensate, i.e., one which has been carried to an intermediate stage of condensation whereby it remains as a resinous material soluble or readily dispersible in aqueous systems while also remaining capable of being converted, under suitable conditions of heat and pressure, to a substantially insoluble and infusible form.

Melamine is the preferred aminotriazine reactant for preparing the heat-curable or potentially heat-curable partially polymerized aminotriazine-aldehyde resinous reaction products Which are used to prepare molded and laminated articles treated according to the practice of the present invention, but other aminotriazines, e.g., mono-, diand tri-substituted melamines, such as the mono-, diand trimethylmelamines, and the like; guanamines, such as formoguanamine, acetoguanamine, benzoguanamine, and the like, as well as mixtures of aminotriazines, may be utilized as reactants. Similarly, formaldehyde, preferably in aqueous solution, is the preferred aldehyde reactant, but other aldehydes, e.g., acetaldehyde, propionaldehyde, bu-tyraldehyde, benzaldehyde, and the like, or compounds engendering aldehydes, e.g., paraformaldehyde, hexamethylenetetramine, and the like, may also be employed. The properties desired in the finished product and economic considerations are among the elements which will determine the choice of the particular aminotriazine and aldehyde employed.

The mol ratio of aldehyde to aminotriazine in such resinous reaction products is not critical, and may be within the order of from about 1.521 to about 4:1, respectively, depending on the nature of the starting materials and the characteristics desired in the final product, but it is preferred that the mol ratio be within the order of from about 2:1 to about 3:1, respectively.

Conventional reaction conditions are observed in preparing the thermosetting aminotriazine-aldehyde resin, i.e., the aldehyde and aminotriazine may be heat-reacted at temperatures ranging from about 40 C. to reflux temperature, i.e., about C., for periods of time ranging from about 30 to minutes, at a pH ranging from about 6.5 to 10, preferably in an aqueous medium. Any substance yielding acidic or alkaline aqueous solutions may be used to regulate the pH, for example, alkaline materials such as alkali metal or alkaline earth metal oxides, hydroxides or salts with Weak acids, e.g., sodium, potassium or calmium hydroxide or sodium or potassium carbonate; mono-, dior trialkylamines, e.g., ethanolamine, triethylamine or triethanolamine; alkylene polyamines or polyalkylene polyamines, e.g., 3,3-iminobis propylamine, and the like, or acidic materials such as hydrochloric acid, sulfuric acid, phosphoric acid, acetic acid, or salts thereof, and the like.

I may also employ other amido or imido compounds having at least two aldehyde-reactable hydrogen atoms attached to amidogen nitrogen atoms besides the aminotriazines in preparing the aminoplast resins used in the heatand pressure-consolidated articles treated in accord ance with the present invention. For example, I may employ urea and those of its derivatives which have been commonly used in the preparation of aminoplast resinous compositions, such as for example the alkylureas, e.g., monoand dimethylurea, halourea, and the like.

The properties of these thermosetting aminoplast resins can be further modified, if desired, by incorporating various other substances into the thermosetting aminotriazinealdehyde resin. Included among such substances are plasticizers such as the a-alkyl-D-glucosides, e.g., amethyl-D-glucoside, disclosed in US. Patent No. 2,773,- 848 to Lindenfelser, methylol derivatives corresponding to the general formula:

wherein R represents an alkyl, aryl or aralkyl group, R represents a hydrogen atom or an alkyl, alkylol, aryl or acyl group, and X represents SO or e.g., N-methylol p-toluenesulfonamide (which may be formed in situ by the addition of p-toluenesulfonamide to an amidogen-formaldehyde reaction mixture) and the like, or combinations of these glucosides and methylol derivatives, e.g., a mixture of a-methyl-D-glucoside and p-toluenesulfonamide, as disclosed in US. Patent No. 2,773,788 to Magrane et al.

The various processes for the preparation of heatand pressure-consolidated molded and laminated articles from aminoplast resinous compositions are so well known in the art that nofurther mention need be made of them here, except to say that aminoplast resinous compositions may be used with any conventional material, e.g., u-cellulose paper, cellulosic fabrics, silk, glass cloth, rayon, nylon, or other synthetic fabrics, and the like, in the preparation of laminates and also that aminoplast resinous compositions may have incorporated therewith for molding purposes conventional fillers, such as tat-cellulose, cellulosic fibers, glass or other synthetic fibers, asbestos, mica, sand, ground cork and the like, mold lubricants, such as,

zinc stearate, glyceryl monostearate, and the like, curing cat-alysts, such as phthalic anhydride, p-tol uenesulfonic acid, 'benzenesulfonic acid, and the like.

In order that those skilled in the art may more fully understand the inventive concept presented herein, the following examples are set forth. These examples are given solely by way of illustration and should not be considered as expressing limitations unless so set forth in the appended claims. All parts and percentages are by weight, unless otherwise stated.

Example I Two hundred parts of hexakis(rnethoxymethyl)-melamine and 200 parts of Epon 1007, a commercially available epoxy resinous reaction product of bisphenol A and epichlorohydrin having a melting point of 127-133 C., an equivalent weight of 190 (grams of resin required to completely esterify one gram-rnol of monobasic acid) and an epoxide equivalent of 1,5502,000 (grams of resin containing one gram-equivalent of epoxide), were charged to a mechanical mixer together with 600 parts of a solvent blend consisting of 39% methyl isobutyl ketone, 35% methyl ethyl ketone, 13% toluene and 13% xylene and blended together until a substantially homogeneous blend was obtained. An amount of a mixture of 65% of the N-methyl morpholine salt of p-toluenesulfonic acid and 35% of free p toluenesulfonic acid sufficient to give 1% of p'toluenesulfonic acid, based on resin solids, in the blend was then thoroughly dispersed throughout the blend, which was then ready for use as a potentially stainretardant composition.

Three hundred parts of the above-described potentially stain-retardant composition were charged to the pressure pot of a De Vilbiss spray gun. A pot pressure of 2.5 p.s.i. (gauge) of clean, filtered air was applied, and an atomizing pressure of p.s.i. (gauge) of clean, filtered air was applied to the spray gun. Next, a clean, dustfree eoffe cup, molded from a commercially available u-cellulose-filled thermo-setting melamine-formaldehyde resin molding composition (-mol ratio formaldehyde: melamine=2:1, respectively), was placed on a rota-ting turntable which, by means of two timers in series, was then brought to a speed of 300 revolutions per minute. At this point the spray gun, which was aimed at the inside and bottom of the cup at an angle of about 30 from the vertical and positioned about 6 inches from the bottom of the cup, was actuated by means of an air-operated solenoid valve for one-half second. Following this spray time the cup, now coated on the inside with the potentially stain-retardant composition, was removed from the turntable and the coating was allowed to level for 45 seconds. Finally, the coated cup was baked in a circulating air oven for minutes at 132 C., removed from the oven, and allowed to cool to room temperature. It had a hard (pencil hardness-15H), lustrous inner surface which was highly resistant to coffee-staining. After repeating the spray-coating procedure on an additional 99 cups, draining the line from the pressure pot to the spray gun, and weighing the pressure pot, it was found that approximately 84 parts of the potentially strain-retardant composition had been used.

In order to demonstrate the coffee-stain resistance of the baked cup, the following accelerated coffee-staining test was carried out. A strong brew of black coffee was prepared by dissolving 32 grams of a commercially available instant coffee in one liter of boiling water. The coffee solution was then cooled to 80 C. and the cup was immersed therein for a period of 144 hours, with the temperature of the coffee solution being held at 80 C. during that time. At the end of the immersion period, the cup was removed from the coffee solution, washed with soap and water and dried. The coated inner surface showed no staining, whereas the uncoated outer surface had become heavily stained and dark brown in color.

10 Examples II-I V The procedure given in Example I was repeated in every detail with one exception, namely, the weight ratios of hexakisfmethoxymethyl)melamine to Epon 1007 epoxy resin were 70:30, 10:90 and 25:75, respectively, rather than :50. In each case, the resulting coatings showed excellent hardness (pencil hardnesses of 41-1 or higher) and luster, and were highly resistant to coffee staining when subjected to the accelerated coffee-staining test described above.

Example V t coated surface of a clean, dust-free, molded melamineformaldehyde resin-containing coffee cup treated in the manner described in Example I was hard and lustrous, and exhibited no coffee stains after being subjected to the accelerated coffee-staining test.

Example VI Fifty parts of the mixture of highly alkoxymethylated melamines employed in Example V (1MF Me and 50 parts of Epon 1009, a commercially available epoxy resinous reaction product of bisphenol A and epichlorohydrin having a melting point of 145455 C., an equivalent weight of I200 and an epoxide equivalent of 2,400- 4,000, were charged to a mechanical mixer together with 186 parts of a solvent blend consisting of methyl isobutyl ketone, 20% toluene and 20% xylene and 2 parts of a commercially available 'butylated melamine-formaldehyde levelling agent and blended together until a substantially homogeneous blend was obtained. Then, 1.5% of phthalic acid, based on resin solids, was added to the blend and thoroughly dispersed therein.

The catalyzed blend was flow-coated on the surfaces of a clean, dust-free coffee cup, molded from a commercially available a-cellulose-filled thermo setting melamine formaldehyde resin molding composition (mol ratio formaldehyde:melamine=2:|1, respectively), and the excess solution was allowed to drain off. Next, the coated cup was air-dried at room temperature for =15 minutes and then baked in a circulating air oven for 10' minutes at 149 C. The resulting clear, colorless thermoset coating had a pencil hardness of 4H and exhibited no coffee stains after being subjected to the accelerated coffee-staining test.

Example VII The procedure of Example VI was repeated in every detail except for the following. The solvent blend employed consisted of 50% methyl ethyl ketone and 50% toluene, and 0.75%, based on resin solids, of p-toluenesul fonic acid was used instead of phthalic acid. The resulting coated coffee cup had a hard, lustrous surface which was highly resistant to coffee-staining when subjected to the accelerated test.

Example VIII The procedure of Example VI was again repeated in every detail except for the following. Fifty parts of hexakis(methoxymethyl)melamine and 50 parts of Epinol H55, a commercially available epoxy resinous reaction product of bisphenol A and epichlorohydrin having a molecular weight of approximately 7,000 and an epoxide equivalent of 0.35 per hundred grams of resin was employed together with 300 parts of a solvent blend con sisting essentially of 60% Cellosolve acetate and 40% methyl ethyl ketone and an amount of a mixture of 65% of the N-methyl morpholine salt of p-toluenesulfonic acid and 35% of free p-toluene-sulfonic acid sufficient to give 1% of p-toluenesulfonic acid, based on resin solids, in the blend. The resulting coated coffee cup had a hard, lustrous surface which was highly resistant to coffeestaining when subjected to the accelerated test.

Example IX Fifty parts of hexakis(methoxymethyl)melamine, 50 parts of Epon 1007 epoxy resin and 18 parts of methyl ethyl ketone were charged to a mechanical mixer and blended together until a substantially homogeneous blend was obtained. Next, 0.5% of p-toluenesulfonic acid, based on resin solids, was thoroughly dispersed throughout the blend, which was then ready for use as a potentially stain-retardant composition.

The required amount of a commercially available acellulose-filled melamine-formaldehyde molding composition (mol ratio formaldehydezmelamine=2zl, respectively) was charged to the cavity of a standard coffee cup mold. The mold was closed and the charge was partially cured by molding at 165 C. under a pressure of 3,000 p.s.i. for 50 seconds. The mold was then opened and 3 grams of the potentially stain-retardant composition were charged to the interior of the pre-molded cup. The mold was again closed and the overglazed cup was cured at 165 C. under a pressure of 3,000 p.s.i. for 50 seconds, following which the cured cup was removed from the mold and allowed to cool to room temperature. It had a 'hard, lustrous inner surface which was highly resistant to coffee-staining when subjected to the accelerated test. In contrast to this, the uncoated outer surface of the cup became badly stained after immersion in the coffee solution for 144 hours at 80 C.

Example X Fifty parts of hexakis(-met-hoxymethyl)melamine and 50 parts of Epon 1009 epoxy resin were blended together on a two-roll mill at a temperature of about 135 C. until a substantially homogeneous blend was obtained. This blend was allowed to cool to room temperature and then passed through a granulating mill. The resulting coarse ground resin, together with 0.5%, based on the weight of the resin, of p-toluenesulfonic acid, was then ball milled until a fine, dry, catalyzed powder was obtained.

A charge of 2.5 grams of this powder was applied to the inner surface of a pre-molded melamine-formaldehyde resin-containing coifee cup in the same manner as the overglazing composition of Example I-X. The resulting cured cup had a hard, lustrous inner surface which was highly resistant to coffee-staining when subjectedto the accelerated test.

It will be obvious to those skilled in the art that other changes and variations can be made in carrying out the present invention without departing from the spirit and scope thereof as derfined in the appended claims.

1 claim:

1. A heatand pressure-consolidated article, prepared from a thermosetting aminoplast resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about to about 70% by weight of a highly alkoxymethylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting. a polyhydric phenol with an epihalohydrin,

12 the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

2. A heatand pressure-consolidated article, prepared from a thermosetting aminotriaZine-aldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by weight of a highly alkoxymethylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

3. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by weight of a highly alkoxy-methylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

4. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resisnous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about 50% by weight of a highly 'alkoxymethyl ated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about to about 50% by Weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

5. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about 50% by weight of a highly alkoxymethylated melamine having from about 5 to 6 methylol groups, of which from about 5 to 6 are alkylated with a lower alkyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 75% to about 50% by Weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

6. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about 50% by weight of a highly alkoxymethylated melamine having from about 5 to 6 methylol groups, of which from about 5 to 6 are alkylated with a lower alkyl group, and

having not more than about one unalkylated methylol group, and correspondingly (B) from about 75% to about 50% by weight of an epoxy resinous material obtained by reacting bisphen01 A with epichlorohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

7. A heatand pressure-consolidated article, prepared from a thermosetting aminoplast resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about to about 70% by weight of a highly methoxymethylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 90% to about by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the t-otalweight of said (A) and (B).

8. A heatand pressure-consolidated article, prepared from a thermosetting aminotriazine-aldehyde resinous composition, coated with a substantially insoluble and intusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by weight of a highly methoxymethylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

9. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by 'weight of a highly methoxymet-hylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) ttrom about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydr-ic phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total Weight of said (A) and (B).

10. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about by weight of a highly methoxymet-hylated melamine having from about 3 to 6 methylol groups, of which from about 3 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 75 to about 50% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

11. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

14 t (A) from about 25% to about 50% by weight of a highly methoxymethylated melamine having from about 5 to 6 methylol groups, of which from about 5 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about to about 50% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

1 2. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) 'from about 25% to about 50% by weight of a highly methoxymethylated melamine having from about 5 to 6 methylol groups, of which from about 5 to 6 are alkylated with a methyl group, and having not more than about one unalkylated methylol group, and correspondingly (B) from about 75 to about 50% by weight of an epoxy resinous material obtained by reacting bisphenol A with epichlorohydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

13. A heatand pressure-consolidated article, prepared from a thermosetting am-ino-plast resinous composition, coated with a substantially insoluble and in-fusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by Weight of hexak-is(methoxymethyl)melarnine, and correspondingly (B) from about to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalodhydrin,

the percentages of said (A) and B) each being based on the total Weight or" said (A) and (B).

14. A heatand pressure-consolidated article, prepared from a thermosetting aminotriazine-aldehyde resinous composition, coated with a substantially insoluble and in fusible cured, adherent, stain-resistant composition r comprising the resinous reaction product of:

(A) from about 10% to about 70% by weight of hexakis(methoxymethyl)melam-ine, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalodhydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

15. A heatand pressure-consolidated article, prepared from a thermosetting melamineaformaldehyde resinous composition, coated with a substantially insoluble and infusible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 10% to about 70% by weight of hexakis(methoxymethyl)melamine, and correspondingly (B) from about 90% to about 30% by weight of an epoxy resinous material obtained by reacting a polyhydric phenol with an epihalodhydrin,

the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

16. A heatand pressure-consolidated article, prepared from a thermosetting melamineaformaldehyde resinous composition, coated with a substantially insoluble and in-fus-ible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about 50% by weight of hexak-is(me-thoxymethyl)melamine, and correspondingly (B) from about 75% to about 50% by weight of an 15 epoxy resinous material obtained by reacting a polyhy-dric phenol with an epihalodhydrin, the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

17. A heatand pressure-consolidated article, prepared from a thermosetting melamine formaldehyde resinous composition, coated with a substantially insoluble and infus-ible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) from about 25% to about 50% by weight of heX-ak-is(methoxy methyl)melamine, and correspondingly (B) from about 75% to about 50% by Weight of an epoxy resinous material obtained by reacting bisphenol A with eplichlorohydrin,

the percentages of said (A) and (B) each being based on the total Weight of said (A) and (B).

18. A heatand pressure-consolidated article, prepared from a thermosetting melamine-formaldehyde resinous composition, coated with a substantially insoluble and infus-ible cured, adherent, stain-resistant composition comprising the resinous reaction product of:

(A) about 50% by Weight of hexakis(methoxymethyl) melamine, and correspondingly New York, 1958, pg. 199.

16 (B) about 50% by weight of an epoxy resinous material obtained by reacting bisphenol A with epichlorohydnin, the percentages of said (A) and (B) each being based on the total weight of said (A) and (B).

References Cited by the Examiner OTHER REFERENCES Skeist, I., Epoxy Resins, Rheinhold Publishing Corp.,

WILLIAM D. MARTIN, Primary Examiner.

A. R. NAVARO, T. G. DAVIS, Assistant Examiners. 

1. A HEAT- AND PRESSURE-CONSOLIDATED ARTICLE, PREPARED FROM A THERMOSETTING AMINOPLAST RESINOUS COMPOSITION, COATED WITH A SUBSTANTIALLY INSOLUBLE AND INFUSIBLE CURED, ADHERENT, STAIN-RESISTANT COMPOSITION COMPRISING THE RESINOUS REACTON PRODUCT OF: (A) FROM ABOUT 10% TO ABOUT 70% BY WEIGHT OF A HIGHLY ALKOXYMETHYLATED MELAMIE HAVING FROM ABOUT 3 TO 6 METHYLOL GROUPS, OF WHICH FROM ABOUT 3 TO 6 ARE ALKYLATED WITH A LOWER ALKYL GROUP, AND HAVING NOT MORE THAN ABOUT ONE UNALKYLATED METHYLOL GROUP, AND CORRESPONDINGLY (B) FROM ABOUT 90% TO ABOUT 30% BY WEIGHT OF AN EPOXY RESINOUS MATERIAL OBTAINED BY REACTING A POLYHYDRIC PHENOL WITH AN EPIHALHOHYDRIN, THE PERCENTAGES OF SAID (A) AND (B) EACH BEING BASED ON THE TOTAL WEIGHT OF SAID (A) AND (B). 